Each plant has within its makeup a process or processes which regulate the growth of that plant. Many of these processes involve the production of ethylene and its interactions with the plant hormonal system.
Ethylene is a simple, unsaturated hydrocarbon compound and is a gas under the normal physiological conditions encountered with growing plants. Ethylene exerts a major influence on many if not all aspects of plant growth, development and senescence. Ethylene is considered a plant hormone because it is a natural product of plant metabolism, acts in trace amounts, acts in conjunction with, or is antagonistic to, other plant hormones, and is neither a substrate nor a cofactor in reactions associated with major developmental processes in plants.
Biochemical and physiological studies of ethylene biosynthesis and mode of action in plants have increased significantly in the past 25 years. Interest and activity in this field has intensified in recent years with the realization that the influence of ethylene is of considerable importance in understanding not only fruit ripening and senescence of plants but also their general hormonal activity.
Ethylene is a powerful natural regulating substance, and its effects can be observed in many areas, particularly during critical periods of the life cycle of higher plants. The influence of ethylene has been observed in practically all aspects of plant growth and development. The physiological effects of ethylene which have been reported are:
1. Stimulation of ripening of fleshy fruits. PA1 2. Stimulation of leaf abscission. PA1 3. "Triple response" of etiolated legume seedlings--reduced stem elongation, radial swelling of stems, and ageotropism or diageotropism of stems. PA1 4. Inhibition of leaf and terminal bud expansion in etiolated seedlings. PA1 5. Inhibition of root growth. PA1 6. Increase in membrane permeability. PA1 7. Stimulation of adventitious root formation. PA1 8. Stimulation of flowering in pineapple. PA1 9. Inhibition of lateral bud development. PA1 10. Causes many types of flowers to fade and deteriorate rapidly, reducing their keeping quality. PA1 11. Interfers with polar auxin transport. PA1 12. Causes abscission of fruit by affecting the abscission cell layer at the fruit/stem junction. PA1 13. Causes epinasty of leaves.
As can be seen from the above, ethylene is an important component in the matrix of hormonal regulatory factors that control plant growth, development, fruiting and senescence.
Many practical uses of ethylene have been developed in the agricultural area, such as degreening of tomatoes, oranges and other fruits to enhance marketing appeal. Ethylene-releasing materials have been developed which increase the flowering of some crops, such as pineapples. Ethylene-releasing agents have been used to make fruits, such as oranges, easier to harvest.
Applications which make use of the benefits derived from the inhibition of ethylene generation have been slower to achieve commercial success. The most significant compounds used for the inhibition of ethylene production in plant tissues are the enol ether amino acid analogs of the L-2 amino 4-alkoxytrans-3-butenoic acid molecules. These are natural products found in the fermentation broths of some microorganisms. The names of three effective amino acid analogs and their microbial origins are (1) Rhizobitoxine from Rhizobium japonicum, (2) Aminoethoxyvinyl glycine from Streptomyces sp. and (3) Methoxyvinyl glycine from Pseudomonas aeruginosa.
Generally speaking, aminoethyoxyvinyl glycine (AVG) is the standard ethylene inhibitor used by those studying the methionine-ethylene forming systems in higher plants.
Most of the compounds which have been identified as having the desired inhibition of ethylene are complex molecules which have been difficult to synthesize, and are therefore expensive.
It is an objective of this invention to provide inexpensive chemical compounds which will inhibit the production of ethylene in plants.
Another objective of this invention is to provide an ethylene inhibitor which acts slowly and provides ethylene-inhibiting properties over an extended period of time.
A still further objective of this invention is to provide a system which will prevent plant senescence so that carbohydrate production is prolonged, and plant yield is increased.
Other objectives include the means and systems to (a) protect flowers and plants from deterioration, especially when shipped in closed containers, (b) increase the yields of plants by preventing flower abortion, fruit drop and abscission of desirable vegetative parts, and (c) improve the quality of turf by maintaining chlorophyll levels, increasing clipping yields, preventing leaf senescence and increasing disease resistance.
Additional objectives and advantages of the invention will appear from the description of the invention that follows.